Circular stapling instruments are well known in the surgical art for bowel surgery. An example of such a device is the Endopath ILS ECS 25 Endoscopic Curved Intraluminal Stapler made by Ethicon Endo Surgery Inc. Many circular stapler patents exist, for example U.S. Pat. No. 4,207,898 to Becht, U.S. Pat. No. 4,351,466 to Noiles, U.S. Pat. No. 5,292,053 to Bilotti et al., and U.S. Pat. No. 5,344,059 to Green et. al.
Currently, many circular stapling instruments employ a design which includes a movable reciprocating drive shaft for adjusting a distance between an anvil assembly and a stapling head assembly and a movable firing bar for engaging the stapling head assembly and firing staples from the stapling head assembly. Both the reciprocating drive shaft and the firing bar slidably engage each other. Therefore, movement between the reciprocating drive shaft and the firing bar results in friction between the reciprocating drive shaft and the firing bar. Sometimes the friction between the reciprocating drive shaft and the firing bar is so high that movement of either the reciprocating drive shaft or the firing bar is deterred or prevented, rendering the circular stapling instrument at least partially inoperable. This is even more relevant in a curved circular stapling instrument wherein the instrument is reusable. Friction can be mitigated in disposable circular stapling instruments by utilizing polymeric materials for components requiring a lower coefficient of friction, or by utilizing lubricants. However, in reusable circular stapling instruments the components are preferably metallic due to the anticipated wear experienced during reuse. Friction-reducing lubricants, if used, will be removed during subsequent cleaning and sterilization steps. Current curved reusable circular stapling instruments do not operate effectively due to increased friction after lubricants wash out after a few reuses, and are a source of malfunction.
As a result it would be desirable to reduce the friction between the reciprocating drive shaft and the firing bar within a circular stapling instrument.